Pseudo photoaffinity labelling

These authors have emphasized that the best way to distinguish between these two possible mechanisms of labeling is by the addition of scavengers of carbenes, nitrenes or whatever the chemical nature of the activated form of the photoaffinity label is. A true photoaffinity label (i.e. one which reacts irreversibly with the same protein molecule to which it was bound at the instant of photolysis) will not be inhibited by added scavengers, whereas a pseudo photoaffinity label (i.e. one which accomplishes derivatization via a reactive intermediate which has been generated in solution) will be. In their studies with nitrenes, Ruoho et al. (1973) found that 10 M p-aminobenzoic acid was an effective scavenger. It should be emphasized that the two possible mechan- 

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